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Transforming growth factor-beta1 resistance in a thyroid cancer model of tumor necrosis factor-alpha resistance
1Thyroid Cancer Research Lab, West Los Angeles VA Medical Center and UCLA School of Medicine, University of California, 90073, USA.
Abstract:
We have shown that both tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) inhibit the growth of the human papillary thyroid carcinoma (PTC) cell line, NPA. In previous work, we developed NPA cells that were resistant to the growth suppressive effect of TNF-alpha, called R30, R45, and R60. In this model there were alterations in the p55 and p75 TNF-alpha receptor signaling in the resistant cell lines. In the present work, we studied the action of TGF-beta1 in this PTC cell model. TGF-beta1 (111 pg/mL) inhibited the proliferation of NPA, R30, R45, and the R60 cell lines by 82.8%, 72.1%, 64.2%, and 24.2%, respectively. On Western analysis, TGF-beta1 reduced c-fos content with similar potency in the NPA and R60 cells. In contrast, TNF-alpha reduced c-fos content in the sensitive NPA cells, but failed to do so in the resistant R60 cells. TGF-beta1 reduced p53 content in the NPA but not in the R60 cells, while TNF-alpha did not affect the p53 content in these cells. Furthermore, the resistant cells had a lower baseline p53 content than the NPA cells. The resistant cells had a significantly increased growth rate. Enzyme-linked immunosorbent assay (ELISA) assays with specific antibody against human p53 showed no apparent increase in the mutant form of p53 in the resistant cells. There were also no mutant forms of Ha-Ras, Arg12p21, Val12p21, Asp12p21, and Asp13p21 detected in the resistant cells. The results showed that R30, R45, and R60 cells are partially resistant to TGFbeta1. The mechanisms of action of TNF-alpha and TGF-beta1 differ in their regulation of c-fos and p53 content. The increase in cell proliferation rate is apparently associated with a decrease of p53 content, but not with mutations of p53 or Ha-Ras.
Insights
Tumor necrosis factor-alpha and transforming growth factor-beta1 inhibit papillary thyroid carcinoma cell growth. Resistant cell lines show partial resistance to TGF-beta1, with differing impacts on c-fos and p53 levels.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Papillary thyroid carcinoma (PTC) is a common endocrine malignancy.
- Tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) are known inhibitors of PTC cell growth.
- Previous studies developed TNF-alpha-resistant PTC cell lines (R30, R45, R60) with altered TNF-alpha receptor signaling.
Purpose of the Study:
- To investigate the effects of TGF-beta1 on a human PTC cell model with varying resistance to TNF-alpha.
- To elucidate the differential mechanisms of action between TNF-alpha and TGF-beta1 in regulating key cellular proteins.
- To explore the relationship between altered protein content, mutations, and increased proliferation in resistant PTC cells.
Main Methods:
- Treatment of sensitive (NPA) and TNF-alpha-resistant (R30, R45, R60) PTC cell lines with TGF-beta1 and TNF-alpha.
- Cell proliferation assays to assess growth inhibition.
- Western blot analysis to measure c-fos and p53 protein levels.
- Enzyme-linked immunosorbent assay (ELISA) to detect mutant forms of p53 and Ha-Ras.
Main Results:
- TGF-beta1 inhibited proliferation in NPA, R30, R45, and R60 cells, with decreasing sensitivity (82.8% to 24.2%) in resistant lines.
- TGF-beta1 reduced c-fos and p53 in sensitive NPA cells, but only c-fos in R60 cells; TNF-alpha affected c-fos in NPA but not R60 cells.
- Resistant cells exhibited increased growth rates, lower baseline p53, but no detectable mutations in p53 or Ha-Ras.
Conclusions:
- PTC cell lines R30, R45, and R60 display partial resistance to TGF-beta1.
- TNF-alpha and TGF-beta1 exert distinct effects on c-fos and p53 regulation.
- Increased proliferation in resistant cells correlates with decreased p53 content, independent of p53 or Ha-Ras mutations.